Earthfall

"At last, the Wetchik tribe is ready to take a ship to the stars. But from the beginning there has been bitter dispute between Nafai and Elemak, Wetchik's youngest son and his oldest. And only Nefai, who wears the Cloak of the Starmaster by the Oversoul's command, understands what this means to the future of all."@en
"Two brothers return to an Earth their ancestors left 40 million years earlier. They are Nafai and Elemak of the planet Harmony, and they are seeking help for their ruling computer which is breaking down. The brothers arrive to find Earth inhabited by winged angels. By the author of The Ships of Earth."
"Two brothers return to an Earth their ancestors left 40 million years earlier. They are Nafai and Elemak of the planet Harmony, and they are seeking help for their ruling computer which is breaking down. The brothers arrive to find Earth inhabited by winged angels. By the author of The Ships of Earth."@en
"The Oversoul, a powerful computer that has the task of watching over the planet Harmony, is failing and must be taken to Earth to be repaired."@en